1. Field of the Invention
The present invention relates generally to improvements in disk drives, and, more particularly but not by way of limitation to improvements in the mounting of transducer heads on actuators by means of which the heads are positioned along surfaces of data storage disks.
2. Brief Description of the Prior Art
In hard disk drives, data is stored on magnetizable surfaces of a plurality of rotatable disks that are mounted in a coaxial stack on a housing of the drive. Transducer heads that read and write the data from and to the surfaces are supported by an actuator that is mounted on the housing and can be moved thereon to position the transducer heads in alignment with data tracks defined on the disks. The support of the heads by the actuator is effected through transducer support arms that are attached to the actuator body and are comprised of leaf members that extend across the surfaces of the disks and are constructed of light sheet steel that will flex sufficiently to permit air swirled by the disks when they are rotated to lift the heads slightly off the disks so that the heads to "fly" across the disk surfaces.
In the past, it has been common practice to attach the support arms to the actuator body using swage plates that form a part of the transducer support arms and are spot welded to the leaf members. The swage plates and the leaf members each have a hole formed therethrough and a tubular boss is formed about the hole through the swage plate on the side thereof that faces away from the leaf member. Bosses on two support arms are then inserted into each of a series of holes formed through a plurality of fingers extending from one end of the actuator body, one boss entering the hole from each end, and a ball is passed through the tubular bosses to force the peripheries of the bosses into tight engagement with the inner peripheries of the holes through the finger. Thus, each finger carries two support arms that are fixed to opposite sides thereof to support two transducer heads in close proximity to two disk surfaces in the assembled hard disk drive.
While this method of mounting transducer heads has worked well in the past, problems have arisen as the need for increased data storage capacity in hard disk drives has grown. As is known in the art, a hard disk drive will often have to meet size limitations that are imposed by the mounting of the drive in the case of a computer. Thus, while the data storage capacity of a hard disk drive might, in principle, be increased by adding disks, in practice, the number of disks has been limited by overall drive size requirements and the necessity of forming a strong connection between the actuator and the transducer support arms. More particularly, to provide a sufficient area of contact between the bosses on the transducer support arms and the inner peripheries of the holes formed in the actuator body, it has been necessary to provide the fingers through which such holes are formed with a thickness that exceeds the thickness necessary to provide support for the transducer support arms and, consequently, to space the disks, one from another, a distance that is greater than would be necessary if the finger thicknesses could be selected on the basis of rigidity considerations alone.
Moreover, it has been found that the conventional method of supporting transducers on the actuator, as described above, gives rise to a second problem. Because of the joining of two transducer support arms to each actuator finger by passing a ball through two bosses in the same hole the finger, an asymmetry exists in the forces that are exerted on the bosses to make the joints. Specifically, the bosses extend in opposite directions with respect to the direction of passage of the ball through the bores of the bosses. Thus, for one transducer support arm, the ball is passed in a direction that will tend to place the boss in compressive stress while, for the other transducer support arm, the direction of passage of the hall will be such to tend to place the boss in tensile stress. It has been found that placing a boss in tensile stress during the swaging operation that joins the transducer support arms to the actuator will often result in a weak joint between the boss and the actuator. In order to prevent tearing of the boss, resulting in a weak joint, the expansion of the boss during swaging must be limited and such limitation will limit the contact forces between the boss and the finger hole periphery to, again, form a weak joint.